The present invention relates generally to tractor hitches and more particularly, to an improved hitch configuration, including a pivotal yoke.
U.S. Pat. No. 4,216,975 discloses a tractor hitch with draft links and a drawbar connected to a bell crank pivotally supported with respect to the rear axle housing of the tractor. The bell crank in the '975 patent includes a relatively long, upwardly extending crank arm and a relatively short, downwardly extending link ear which is coupled to the draft links, the drawbar and the sway links. A bell crank actuator, with or without load sensing, is then coupled between the tractor frame and the upper end of the crank arm to pivot the bell crank to adjust the position of the draft links and the drawbar. In such a hitch, the pivotal support of the bell crank must support substantial force loads, including a substantially horizontal component due primarily to the draft force transmitted to the hitch from the implement. This force loading produces frictional losses which create an undesirable hysteretic error effect with respect to the draft sensing performance of this hitch arrangement. Another problem is that the '975 drawbar is pivotally coupled to the bell crank at the fore end of the drawbar, while the aft end of the drawbar is supported by the coupler support, thus limiting the drawbar to only horizontal fore-and-aft movement as the bell crank pivots. The '975 hitch arrangement also suffers from a lack of compactness which could prevent its use on certain types of two-wheel drive tractors unless substantial modifications are made. The '975 hitch also requires a relatively long actuator stroke to achieve a relatively short fore-and-aft movement of the draft links and drawbar because the crank arm is substantially longer than the link ear.